“The vibration of His flute is just like a bird that creates a nest within the ears of the gopīs and always remains prominent there, not allowing any other sound to enter their ears. Indeed, the gopīs cannot hear anything else, nor are they able to concentrate on anything else, not even to give a suitable reply. Such are the effects of the vibration of Lord Kṛṣṇa’s flute.” (Madhya-lila 21.144)
…This vibration of Kṛṣṇa’s flute is represented by the Hare Kṛṣṇa mahā-mantra. A serious devotee of the Lord who chants and hears this transcendental vibration becomes so accustomed to it that he cannot divert his attention to any subject matter not related to Kṛṣṇa’s blissful characteristics and paraphernalia. (from purport)
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The Hare Krishna Movement 